feat(landing): Russian default + SEO head, icons and OG card

The landing now always opens in Russian (saved 🌐 choice still wins) —
browser-language detection made the indexed content nondeterministic
(Googlebot renders with en-US). landing.html gains the static Russian
SEO head: title/description, canonical pinned to the production origin,
Open Graph card (Telegram/VK link previews), twitter:card, JSON-LD,
theme-color and the favicon set; the SPA shell turns noindex and its
tab title becomes «Эрудит (Скрэббл)». New assets/icons generator
(same tile design as the VK loader) produces favicon.svg/ico,
apple-touch-icon.png and og-image.png into ui/public/, plus robots.txt.

ui/src/Landing.svelte

@@ -1,7 +1,7 @@
 <script lang="ts">
   import { onMount } from 'svelte';
   import { applyTheme } from './lib/theme';
-  import { i18n, localeFrom, setLocale, t, type Locale } from './lib/i18n/index.svelte';
+  import { i18n, setLocale, t, type Locale } from './lib/i18n/index.svelte';
   import { loadPrefs, savePrefs, type Prefs } from './lib/session';
   import { aboutContent } from './lib/aboutContent';
   import { telegramChannelLink, vkAppLink } from './lib/landing';
@@ -9,7 +9,8 @@
   // Standalone landing page, the public entry at "/" (the game SPA lives at /app/ and
   // /telegram/). It reuses the app's theme/i18n/prefs leaf modules — not the app store — so it
   // stays light. Theme is EPHEMERAL here (no auto, no persistence): it starts from the system
-  // scheme and the icon toggles light<->dark in memory. Language IS persisted (synced with the app).
+  // scheme and the icon toggles light<->dark in memory. Language IS persisted (synced with the
+  // app) but defaults to Russian, never to the browser language — see landing.ts.
 
   let theme = $state<'light' | 'dark'>('light');
   let langOpen = $state(false);
@@ -31,7 +32,13 @@
     prefs = await loadPrefs();
     theme = systemTheme();
     applyTheme(theme);
-    setLocale(prefs.locale ?? localeFrom(typeof navigator !== 'undefined' ? navigator.language : 'en'));
+    setLocale(prefs.locale ?? 'ru');
+  });
+
+  // Keep the document language honest for assistive tech and crawlers: the static shell
+  // declares lang="ru" (the default), and a 🌐 switch to English must follow.
+  $effect(() => {
+    document.documentElement.lang = i18n.locale;
   });
 
   function toggleTheme(): void {

ui/src/landing.ts

@@ -1,7 +1,16 @@
 import { mount } from 'svelte';
 import './app.css';
+import { setLocale } from './lib/i18n/index.svelte';
 import Landing from './Landing.svelte';
 
 // Entry for the standalone landing page (served at "/" by the gateway; the game SPA lives at
 // /app/ and /telegram/). Mounts into the same #app node as the SPA's main.ts.
+
+// The landing always starts in Russian — the primary audience and the language of the
+// static SEO head (crawlers render with arbitrary navigator.language, e.g. Googlebot's
+// en-US, so browser detection would make the indexed content nondeterministic). Set
+// before mount so the very first paint is Russian; a saved 🌐 choice is applied in
+// Landing's onMount once prefs load.
+setLocale('ru');
+
 export default mount(Landing, { target: document.getElementById('app')! });